An ongoing concern in the elevator industry is the situation where an elevator car stops between floors due to a power failure, equipment breakdown, or for some other unforeseen circumstance. Existing codes require that either the elevator car doors or hoistway doors cannot be opened more than four inches from inside the car whenever the car is outside the landing zone. These standard codes also require that when the car door is arranged so that it cannot be opened, the car door shall be openable from outside the car without the use of special tools.
Elevators typically employ door coupling mechanisms which mechanically couple the car doors to access doors located at the passenger landings, so that both the car door and the access door can be simultaneously and jointly controlled to open or close to allow for entry and exit of passengers. One such existing door coupling mechanism is the blade-and-roller-type mechanism employed on elevators manufactured by Otis Elevator Company. This coupling mechanism is illustrated in FIGS. 1 and 2.
Various mechanical car door locking systems have been developed which are integrated with the car door coupling mechanism. One example, shown in U.S. Pat. No. 1,326,440, entitled "Apparatus for Operating an Interlocking Landing in Cage Gates of Elevators," issued to Shaudoir, shows an elevator/hoistway door coupling mechanism employing a mechanical interlock which prevents the elevator door and/or hoistway door from opening unless the elevator car is in the desired position at a hoistway landing.
Another example, U.S. Pat. No. 4,313,525, entitled "Car Door Safety Interlock," issued to McDonald, discloses a power operating sliding door of an elevator car which is provided with a mechanical safety interlock which restrains the elevator car door from opening unless disengaged through a mechanical interconnection responsive to the motion of a door coupling vane contacting a pair of hatch door rollers.
U.S. Pat. No. 4,423,799, entitled "Vehicle Door Lock for Limiting Door Opening to Specified Vehicle Positions," issued to Glaser, et al., similarly discloses a variety of locking mechanisms which restrain elevator car doors from opening unless disengaged as an indirect result of the engagement of the elevator car door/hoistway door coupling mechanism.
These and other existing mechanical interlock systems, however, typically utilize several interconnected moving parts and are difficult or impossible to retrofit on existing elevator systems.
One object of the present invention is, therefore, to provide a mechanical car door interlock which employs few moving parts.
Another object of the present invention is to provide a mechanical car door restraint which is integrated with a conventional blade-and-roller type door coupling mechanism so that the elevator door coupling vane serves the additional functions of position sensor and actuator for the elevator car door interlock.
It is yet another object of the present invention to provide a mechanical door interlock which is simple in design and operation, to facilitate easy installation, service, and retrofitting of the device onto existing elevator systems.
It is yet another object of the present invention to provide a mechanical door interlock which may be quickly and easily disengaged from outside the elevator car.